Wastewater conveyance systems have been essential to the health and prosperity of our society. Throughout past decades, sewers have been utilized to efficiently transport wastewater, or sewage, from homes and businesses where it was generated, to wastewater treatment plants, which use various processes to transform the wastewater into an environmentally-safe fluid waste stream and a solid waste suitable for disposal or reuse. Similarly, stormwater conveyance systems are used to transport surface runoff to suitable discharge points into the environment. Modern or modernized water systems have separate sewage and storm conveyance systems, while older systems sometimes have combined sewage and stormwater conveyance systems, which deliver these waters to a treatment plant.
Wastewater and stormwater carried from homes and businesses eventually enters a large pipe called an interceptor, which carries the flow to a treatment plant or discharge point. The interceptor is generally located at the lowest possible elevation so that gravity, can be utilized as much as possible to move the massive volumes of water.
Turbulence in wastewater flow is a main cause of odorous and corrosive gas emission and abrasive wear of the underground conveyance structures. Engineers are therefore careful to design the conveyance network so that under various conditions the flow within the pipes remains tranquil, without turbulence. Typical design guidelines call for less than 1% slope to keep the velocity and turbulence in pipelines low, and gas emissions and abrasive wear to a minimum. Practically, however, terrain is not flat and turbulence cannot be eliminated from the network. To avoid steep slopes or very deep and expensive excavation, sewer drops are inevitable. The drops themselves are essentially waterfalls within a vertical well or structure. Drops are inherently turbulent, but are still preferred over sloped piping because they concentrate the turbulence at one point, rather than over miles of steeply-sloped piping. Every sewer drop is thus a selected point of flow energy release, and consequently, a source of odor and corrosion, and mechanical wear of the conveyance system.
One approach for dealing with the adverse consequences of flow drops has been proposed in U.S. Pat. No. RE40,407, incorporated by reference herein. U.S. Pat. No. RE40,407 describes a vortex drop structure and technique for conveying flow from a higher elevation to a lower elevation by accelerating and redirecting the flow into a generally helically-spiraling path along an interior wall of a vortex shaft. Typically, the vortex shaft is has a generally-circular cross-section and is situated generally vertically, (although the device may function in other non-vertical orientations, including in a horizontal orientation). In a properly-designed vortex drop structure, the flow spirals downward inside of the vortex shaft while under the influence of centripetal forces; therefore, the flow tends to maintain intimate contact with the interior wall of the vortex shaft. Under these conditions, in the center of the vortex shaft's cross section (for at least the majority of the height of the flow drop) is a stable air core, even when the vortex drop structure is conveying flow at its design flow capacity. In certain exceptional situations, the vortex shaft may work without an air core.
In wastewater or stormwater conveyance systems, the flow created by the vortex drop structure provides a number of benefits, including protecting the life of the drop structure by virtually eliminating abrasion and dissipating energy, controlling emissions of odors by dragging ambient air downwards with the flow, and even improving the characteristics of the wastewater or stormwater by aerating it using the dragged-down air. However, vortex drop structures may be used in industrial processes, and elsewhere, wherever an energetic flow needs to have its kinetic energy dissipated.
It has been proposed to utilize the vortex drop structure and its well-controlled flow characteristics to generate electrical energy. The energy which may be dissipated in sewer and stormwater collection system flow drops, and elsewhere, can collectively produce substantial amounts of energy, which in turn may be used to power industrial processes or simply feed into the electrical grid for general use by power company customers.
Although the concept of generating power using vortex drop structures is a promising one, to date, an efficient an effective solution for power generation using vortex drops has not been proposed. Accordingly, a need exists for a practical power generation solution.